Valve tappet with temperature responsive clearance compensation



y 9, 1956 o. B. CAMPBELL 2,747,559

VALVE TAPPET WITH TEMPERATURE RESPONSIVE CLEARANCE COMPENSATION FiledJuly 15, 1953 Fig .1 "i f 3 INVENTQ 05mm: E CAMPBELL ATTORN UnitedStates Patent VALVE TAPPET WITH TEMPERATURE RESPON- SIVE CLEARANCECOMYENSATIQN Osmon B. Campbell, St. Joseph, M0.

Application July 13, 1953, Serial No. 367,672

2 Claims. (Cl. 12390) The invention relates to the valve mechanism ofinternal combustion engines and is particularly concerned withmaintaining a predetermined clearance in the mechanism in spite of thechanges in temperature of the parts, which takes place during operationof the engine.

Due to the lengthening which occurs, particularly, in the valve stem,when the engine heats up, quite a large clearance must be provided tomake sure that the valves will seat at maximum temperature. Although thetemperatures of the different parts of a valve and its gear differwidely, they bear a definite relation to each other, and I use thisrelationship to maintain the desired clearance throughout the changes intemperature.

I use a temperature sensitive mechanism, preferably within the valvelifter, to ofiset the changes in length of the valve stem, as itundergoes changes in temperature.

Referring to the drawing, Fig. l is a vertical section of the lifterthrough the middle of the slots in the head of the vertical member. Fig.2 is a side view of one of the thermal elements. Fig. 3 is a top view ofone of the wedges. Fig. 4 is a top view of the head of the verticalmember.

I have shown a valve lifter comprising a cylindrical body member 1having a longitudinal bore, said body being closed at the bottom andopen at the top, a vertical member 2, with a flattened top 3, extendingupward from the bottom, a pair or a plurality of pairs of metal pieces4, which are thinner at one end than the other, so that they are wedgeshaped, rest upon the flattened top and are adapted to abut the valvestem. Bimetallic thermal elements 5, one on each side of the verticalmember, are fixed at one end thereto and engage, preferably, the thickends of the wedges with their other ends. The extended portion 6, ofeach thermal element engages half of the wedges through the hole 7, andis slidable in the slot 8, in the other Wedges. By this means the wedgesare held in good alignment.

With changes in temperature, flexing of the thermal elements will movethe Wedges in and out, varying the total thickness of metal in theclearance. Necessarily,

the thermal elements cannot move the wedges, when the cam is engaged andthe valve is off its seat, but a definite, very small clearance isprovided in the mechanism, so that the pressure is OE and the wedges arefree to move once during each revolution of the cam. The length ofmovement of the wedges is not great and is far below the elastic limitof the thermal elements, so that they are not damaged by beingtemporarily restrained.

When designing the device for any engine, the correct cold clearance forthat engine, when using tappets with a fixed setting, must be known.Then provide such a relation between the length of travel of the wedges,their taper, and the number to be used, that their action will shortenthe effective length of the lifter by the amount of the above mentionedknown clearance, when the lifter reaches its maximum temperature.

I have found that any engine cam striking a litter, even with zeroclearance, is slightly audible and that with the minimum clearancepermissible to insure that the valve will seat, the impact of the valveupon its seat is distinctly audible. I have also found that a clearanceof about two thousandths inch does not seemingly increase the sound.

While quiet operation is a feature of this invention, it is not by anymeans as important as the constant correct timing, which is attained byits use.

I claim:

1. A valve lifter comprising a cylindrical body member having an axialbore, said body being closed at the bottom and open at the top, a secondmember with flattened top extending upward from the bottom, a pair ofwedges movably supported upon said flattened top of the second member,two thermal elements, one on each side of the second member, affixed atone end to said second member, and each engaging one of the wedges atits other end, all in combination and in operative relation to vary thetotal thickness of the wedges in the clearance, when flexing of thethermal elements occurs in response to changes in temperature.

2. A valve lifter comprising a body member having an axial bore, closedat one end, a standard therein, at least one pair of wedges supported bythe standard, slidably movable one upon the other across the axis of thebore, and temperature sensitive elements attached to the standard andengaged with the wedges, so that the wedges will be caused to move uponflexing of the elements.

References Cited in the file of this patent UNITED STATES PATENTS1,531,909 Engemann Mar. 31, 1925 1,637,020 Fekete et al July 26, 19271,689,801 Pope Oct. 30, 1928 1,692,435 Clemenson Nov. 20, 1928 1,696,361Reich Dec. 25, 1928

